Japanese Knotweed: Identification and Effective Control Methods

That aggressive plant taking over your yard? It's Japanese knotweed (Polygonum cuspidatum, also called Mexican bamboo). It's on virtually every invasive species list in North America for good reason: it spreads rapidly via rhizomes, forms dense thickets, and chokes out native vegetation. The wispy white flowers in fall are attractive, but don't let that fool you.

How to Kill It

Digging works for small patches, but any rhizome fragment left behind resprouts. For established stands, use the "cut-and-daub" method in late summer: cut stems near the ground, then immediately apply undiluted glyphosate (Roundup, Kleenup) to the fresh cuts. For even better absorption, peel back a few strips of bark near the base with a kitchen peeler before applying herbicide—this exposes vascular tissue for faster uptake.

Persistence is key. Monitor for regrowth and retreat as needed. Bag and dispose of all plant material; never compost it.

Polygonum cuspidatum

Polygonum cuspidatum

Polygonum cuspidatum

Polygonum cuspidatum